1. Field of the Invention
This invention relates generally to communication systems. More particularly, the invention relates to an improved architecture for implementing communication protocols such as the “Bluetooth” wireless protocol.
2. Description of the Related Art
Various combinations of hardware, firmware and software may be used to implement wireless and terrestrial communication protocol stacks. For example, referring to FIG. 1, the “Bluetooth” specification is comprised of several different protocol layers including a radio frequency (“RF”) layer 160, a baseband layer (“BB”) 150, a link control layer (“LC”) 140, a link manager layer (“LM”) 130, a logical link control and adaptation protocol layer (“L2CAP”), and a serial line emulation layer (“RFCOMM”). The functionality of each of these layers (as well as additional Bluetooth protocol layers) is described in detail in Bluetooth Protocol Architecture, Version 1.0 (Aug. 25, 1999) (“Bluetooth Protocol Architecture”), which can be found at “http://www.Bluetooth.com.”
Briefly, Bluetooth is a short-range radio standard intended to replace the cables connecting portable and fixed electronic devices. The standard, which operates in the unlicensed Industrial-Scientific-Medical (“ISM”) band at 2.4 GHz, focuses on robustness, low complexity, low power, and low cost. Within the RF layer 160, a frequency hop transceiver is applied to combat interference and fading and a shaped, binary FM modulation is applied to minimize transceiver complexity. A symbol rate of 1 Ms/s, is maintained with a slotted channel having a nominal slot length of 625 ms. For full duplex transmission, a Time-Division Duplex (“TDD”) scheme is used. Information is exchanged through data packets, with each packet being transmitted on a different hop frequency. A packet typically covers a single slot, but can be extended to cover up to five slots, depending on the application. Additional features of the Bluetooth standard are described in Jaap Haartsen, Bluetooth—The Universal Radio Interface for ad hoc, Wireless Connectivity, ERICSSON REVIEW No. 3, (1998).
As illustrated in FIG. 1, a Bluetooth integrated circuit (“IC”) 106 is typically configured to implement the lower layers of the Bluetooth protocol stack (e.g., the RF 160, BB 150 LC 140 and LM 130 layers). The Bluetooth IC 106 in this example is typically an Application Specific Integrated Circuit (“ASIC”), a chip custom designed for a specific application (in this case the Bluetooth protocol). ASICs improve performance over general-purpose processors because ASICs are “hardwired” to do a specific job and do not incur the overhead of fetching and interpreting instructions stored in memory. As such, an ASIC chip typically performs an electronic operation as fast as it is possible to do so, providing that the circuit is efficiently designed.
The Bluetooth IC in FIG. 1 communicates with a host processor environment 105 through a host interface 107. The host processor environment 105 is typically comprised of a general purpose CPU (e.g., an Intel Pentium®-class processor) and software executed by the CPU (e.g., an operating system with an application programming interface (“API”) and one or more application programs). As shown, in a typical configuration the host processor environment 105 is configured to support only the upper layers of the protocol stack, RF Comm 110, and L2CAP 120.